1. Field of the Invention
The present invention relates to golf club heads, more particularly to hollow metallic wood club heads.
2. Description of the Prior Art
In a recent development of wood clubs such as a driver and fairway clubs, there have been proposed various kinds of "metalwoods", in which the head has the shape of a traditional wood but formed of metal such as stainless steel or aluminium alloy, molded in a hollow form by the lost-wax casting process. The hitting surface or "face" of the metallic head is formed at a loft angle preselected in accordance with the number of the wood club. Since the loft angle at the moment of impact is retained at the preselected angle, the golf ball is applied with back spin and tends to be floated up by the lift force acting thereon in the air, resulting in decrease of its flight distance or carry and decrease of its run after drops on the ground.
During the lost-wax casting process, it is extremely difficult to control the grain size of the metal structure. As a result, the grain size of the metal structure becomes relatively large, resulting in deterioration of the rigidity of the metallic head. Since the shell of the hollow metallic head may not be thinned for the foregoing reason, the metallic head may not be enlarged without causing any increase of its weight. Accordingly, the sweet spot area of the metallic head is, in general, narrow, and the directional stability of the ball is poor.